Chemical control of weed is a most economical and effective means for controlling weeds in farmlands. However, continuously use of a single chemical herbicide or chemical herbicides having a single functional mechanism at a high dosage for a long period of time is likely to cause problems associated with evolved drug resistance and tolerance of weeds. Well complexing or formulating of herbicidal compounds can achieve the following advantages: expanding weed spectrum, improving weed control effect, and delaying occurrence and development of drug resistance and tolerance of weeds, and thus is one of the most effective means to solve the above problems.
The hydroxyphenyl pyruvate dioxygenase (HPPD) is another novel herbicide following the acetyl CoA carboxylase (ACCase) inhibitor, the acetolactate synthase (ALS) inhibitor and the Protox inhibitor etc. The HPPD inhibitor has a broad spectrum of herbicidal activity, can be used before and after budding, and may cause albinism and death of weeds. Although the HPPD inhibitor result in similar poisoning symptoms to that of carotenoid bio-inhibitors, it is markedly different from the known carotenoid bio-inhibitors in terms of chemical properties such as polarity and ionization degree etc.
The risk of resistance of weeds to HPPD inhibitor herbicides is significantly reduced compared to that of ACCase inhibitors, and HPPD inhibitor herbicides and commonly used ACCase inhibitors or ALS inhibitors having other mechanisms of action do not have cross-resistance caused by target resistance.
Herbicide safener, also known as antidote or protectant, is a chemical substance with unique properties. Herbicide safener selectively protects crops from damage caused by herbicides without affecting the activity of the herbicides against target weeds, thereby enhancing the tolerance of crops to the herbicides and increasing the safety of herbicides for crops. Herbicide safeners have been extensively researched in the United States, Germany, Switzerland, Japan, Canada, Russia, South Korea, and Hungary, while this research started late and did not begin until the late 1980s in China.
Herbicide safeners can be divided into dichloroacetamides, oxime ethers, carboxylic acid derivatives, sulfonic acid derivatives, oxazoles, thiazoles and other heterocyclic compounds, ketones and derivatives thereof etc., according to category of compounds; the herbicide safeners can be divided into naphthalic anhydrides, dichloroacetamides, oxime ethers, heterocyclic compounds, sulfonylureas (sulfonamides), plant growth regulators, herbicides and fungicides etc., according to structure; and herbicide safeners can be divided into combination types, decomposition types, antagonism types, compensation types and the like, according to the action mode and action mechanism.
With the wide application of herbicides, the problem of damages caused by herbicide continues to emerge, and there is an urgent need for herbicide safeners. Herbicide safeners include amides, carbamates, phenoxycarboxylic acids, aryloxyphenoxypropionates, sulfonylureas, sulfonamides, imidazolinones, cyclohexanediones, isoxazoldiones, s-triazines, and the like. The protected crops mainly include corn, rice, sorghum, rye, cotton, soybean, and so forth.
At present, the herbicides used in cornfields mainly include a few of products such as nicosulfuron and mesotrione etc. These two herbicides have been applied on corn for many years, and the resistance of weeds to nicosulfuron has become prominent. Mesotrione has a low activity, a narrow weed controlling spectrum, and especially a poor effect on controlling Setaria weeds. Accordingly, products which have a high safety and a broad weed controlling spectrum and can be used to solve the problem associated with resistant weeds are urgently needed.